Current-induced magnetization switching in MgO barrier based magnetic tunnel junctions with CoFeB/Ru/CoFeB synthetic ferrimagnetic free layer

TL;DR

This paper investigates the critical current density and thermal stability in MgO-based magnetic tunnel junctions with a synthetic ferrimagnetic free layer, revealing that strong antiferromagnetic coupling reduces current requirements without compromising stability.

Contribution

It introduces a method to determine critical current density and thermal stability using Slonczewski's model in MgO tunnel junctions with a CoFeB/Ru/CoFeB free layer.

Findings

High antiferromagnetic coupling reduces critical current density.

Thermal stability remains high despite reduced current density.

Analysis aligns with thermal fluctuation considerations.

Abstract

We report the intrinsic critical current density (Jc0) in current-induced magnetization switching and the thermal stability factor (E/kBT, where E, kB, and T are the energy potential, the Boltzmann constant, and temperature, respectively) in MgO based magnetic tunnel junctions with a Co40Fe40B20(2nm)/Ru(0.7-2.4nm)/Co40Fe40B20(2nm) synthetic ferrimagnetic (SyF) free layer. We show that Jc0 and E/kBT can be determined by analyzing the average critical current density as a function of coercivity using the Slonczewski's model taking into account thermal fluctuation. We find that high antiferromagnetic coupling between the two CoFeB layers in a SyF free layer results in reduced Jc0 without reducing high E/kBT.